Mark Hollis lives less than a quarter mile from where the train track crosses Pat Thomas Parkway in downtown Quincy. He hears freight trains go by his house nearly every day.

But what he heard Tuesday morning didn't sound normal.

“It was about 6:40 when I got up and I heard a train running, like it was going way too fast, and all the sudden it started making a loud, thunder-like sound,” Hollis said. “So I came to the road and looked over there, it was all laying on its side.”

Hollis, who was up early smoking a cigarette outside, heard the commotion as a CSX freight train derailed. He called 911 as fast as he could.

Quincy police officers and fire fighters on the scene initially advised onlookers the substance was hazardous and ordered them to stay 75-100 feet away from the rail cars. Gadsden County Sheriff's Office at the time misidentified the substance as acetic acid, the main component of vinegar, but CSX later said it was something else.

"Two of the rail cars spilled a small amount of adipic acid, which is a solid chemical commonly used in the production of gelatin food products," the company said. "While this product poses no safety risk to the public, CSX contractors on site are taking standard precautions as they work to clean up the area."

The Federal Railroad Administration will lead an investigation into the cause of the derailment. The agency was on scene by Tuesday afternoon.

PubChem, a National Institutes of Health chemistry database, describes adipic acid as a white crystalline solid that is insoluble in water.

"The primary hazard is the threat to the environment," the NIH website states. "Immediate steps should be taken to limit its spread to the environment. It is used to make plastics and foams and for other uses."

As a result of the derailment, Pat Thomas Parkway was blocked for most of Tuesday as crews brought in cranes to remove the rail cars, said Maj. Shawn Wood of the Gadsden County Sheriff's Office.

A CSX cleanup team collects adipic acid that leaked from a train car that derailed in downtown Quincy Tuesday morning. The powdery substance posed a very low risk to passersby.(Photo: Hali Tauxe/Democrat)